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You can construct a solar powered boombox for as little as $75

Combine a small, energy efficient digital amplifier, cheap bookshelf speakers, batteries, a small solar panel, and your MP3 player as a source.

Fasten everything together, add a handle, and take it on the road!

This project makes for a fun, easy solar project, that will help you learn about how solar panel, and audio systems operate.

Assembly has been simplified as much as possible, with a very high quality product as the end result.

Possible applications-

iPod or Mp3 amplifier

"Off grid" remote or cabin audiophile system

Third world use

Eco friendly sound system for outdoor events

Science fair or educational project

Jobsite radio and tool battery charger

Laptop amplifier for music and movies

The Sonic Impact digital amplifier has been raved about by audiophiles. It has the added benefit of using less electricity than a conventional solid state amplifier, which makes the battery last longer, and the required solar panel smaller.
It is capable of driving most home stereo speakers, so feel free to try it with any speakers you may have on hand. The results may surprise you!
Some speakers are more efficient than others and will play louder given the same input.

*Sonic Impact fans note*

A Sonic Impact amplifier ($30) will run directly off of a single Harbor Freight car charging solar panel($10-20) without a battery.
I offer no guarantees here, but in July Wisconsin sun, an unmodified SI amp was connected directly to the solar panel (a stock SINGLE Harbor Freight unit) and speakers. I did this repeatedly with no problems, other than that the music stops when clouds interfere, or the panel is shaded.

THIS MAKES A GREAT DEMONSTRATION!

The reason this is remarkable is that the voltage of the panel is over the maximum the amp is supposed to take. The load presented by the amp, draws the voltage down before the amp is damaged.
I have tested this extensively, but you try this at your own risk!

A more powerful panel, such as the double unit we use on the DelSol will be more likely to produce enough current to damage the amp.
I later modified the amplifier to improve the bass, and it required more current than the single panel provided.

Add a battery, and you have a more functional simple system.

See ELECTROVOX.COM for more info, links, and advanced systems.

Step 1: Parts, Sources and Tools

Most components are available via Parts Express, but I list multiple options for some components.

Amplifier options -

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-380
Dayton amp - $45
(This amp should be functionally identical to the Sonic Impact amp mentioned throughout this instructable)

An alternative amplifier is sold on Ebay by a seller in China. Shipping will take a while, but the basic amp board is only $25 shipped. Using this amp is a slightly more advanced project, and may require some additional parts. Go to http://stores.ebay.com/Sure-Electronics and search for TA2024
Parts express now carries this amplifier as well-
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-308

Solar Panel-

http://www.harborfreight.com/15-watt-solar-battery-charger-44768.html -$10-19 Your Local Harbor Freight will match website sale prices if you print out the web page and take it into the store.

Speakers-

White indoor/outdoor speakers shown on intro page - $24
I Highly recommend recycling some old speakers here. Car speakers can be used if you provide an enclosure. Use high quality bookshelf speakers if you're an audiophile.

bag phone battery charging clip
bag phone battery These can be found for a lot less sometimes.

Cordless drills can be a battery source if the voltage is under 13.6 volts

Optional-get 8-10 AA NIMH 2400mAh or larger. Eight fit in the SI amp, but building 10 into a custom pack will play louder than even the lead acid batttery!
I don't provide instructions for these options yet, however.

Misc.

Wire is mostly recycled, but silicone wire is recommended for connecting the battery to its plug. Cheapskates can try lamp cord here, but please be careful. and read the warnings on the next pages.

Harbor Freight has digital multimeters for $3 - 10.00 that are very useful, but optional.

TOOLS -

Soldering Iron
wire cutters/strippers
needlenose pliers
screwdrivers

Step 2: Wiring & Assembly

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There are really only a few basic steps here-

1. Remove diode from cigarette plug. (picture 3)

Desolder the diode from inside the Cigarette plug connector that comes with the Solar Panel. The diode prevents the battery from discharging through the solar panel when the solar panel's output is low. The diode must be oriented as shown, with the line away from the solar panel. (see pic 3)

2. Construct a plug/jack passthrough, connect it to the diode and solar panel.

Pay very close attention to wire polarity! You can damage your amp by connecting power backwards! The wire with the white stripe is positive, the black wire is negative. Red terminals are positive, black is negative. Center terminals are positive.

DC jacks often have a switched terminal that we will not be using. It is easy to mistake this for the negative terminal. To find this terminal, insert a plug into the jack and test for continuity. only one terminal will be connected to negative on the plug. The center positive terminal should be obvious. The third terminal is not used, and may be broken off to simplify things.

I created the plug/jack that is attached to the solar panel by bending the terminals on each until they would make contact, then soldering them together and connecting the diode/wires last.
Arrange the parts so that the positive connections have No Chance of coming into contact with the negative. This is very important.
I've had a small battery melt through a small amount of insulation and start smoking. These small batteries pack a lot of juice, and could burn your house down. I'm not kidding. Be sure and do a good job soldering this plug, and on the battery plug. Make sure that soldered connections are solid, and that the bare portions of the wire are kept to a minimum and cannot come into contact with each other. Test all systems in an open area, and don't trust your battery until you've spent some time with it and it hasn't melted anything.
battery meltdown
I now use silicone wire as a result. 14 AWG is a good size.

3. connect a DC plug to the battery.

Wire the DC plug onto the battery wires before connecting the wires to the battery. Center is positive on the plug. Use heavier wire than elsewhere. I suggest at least 16 AWG lamp cord. reread the warning in the above paragraph, and make sure and wire in a fashion so that the bare wires cannot bend and make contact.

4. Test the system prior to assembling the components into a boombox.

Connect amp to the speakers using 22AWG wire. Some speakers have this attached already.
Plug the battery into the solar plug/jack, then plug the solar plug/jack into the amp .
Connect the sound source to the amp.
turn amp on.
turn sound source on.
adjust volume.

I'm not going to go into physical assembly, since everyone's will be different .
Make sure and attach everything together into a solid unit.
Dangly, or loose bits suck.
In this application.

Enclosing everything in a ready made box such as a toolbox or a small cooler can work well, especially if you want to use old car speakers.

Having the solar panel and battery easily removable is very handy. I use Velcro.

Handle options
I've used a bar clamp to hold bookshelf speakers together temporarily.
A wire handle from a five gallon bucket can be fitted.
A handle needs to fold out of the way of a top mounted solar panel. Shading the panel, even a little, reduces its output significantly.

You should be able to add an ipod dock with charging capability by modifying these instructions.

Step 3: Using your Solar Boombox

Larger solar panels require charging circuitry to regulate the charge current and protect the battery from overcharging. Our solar panel is small enough that a charge controller isn't required.

The battery and solar panel are removable so that you can remove the battery and solar panel and set them outside to charge with less concern for the weather and theft. You could also have two batteries and have one charging outside, while you use the boombox inside, or in shade.

Batteries will last longer if kept in a charged state.
Try to keep lead acid (SLA) batteries fully charged, and never allow voltage to fall below around 9.6 volts (The amp will stop working at around this voltage)
NIMH batteries can be fully discharged without damage, but also should be kept charged for best results.
If your battery will not be used for a while, its charge should be topped off periodically, either by leaving in a sunny spot with the solar panel attached, or by using a wall charger.
I would do this monthly with a SLA battery, and biweekly with NIMH.

Read this instructable for some basic solar battery charging information.

Putting a bead of silicone caulk around the glass on your solar panel is recommended to help weatherproof it.

Different audio sources have different output levels. If you feel your box is too quiet, the source may not put out strong enough of a signal.

You should be able to turn the amplifier nearly all the way up, and control the volume with your source, assuming it has a volume control. You can experiment with different combinations with the two volumes in order to get the best sound.

Keep the solar panel oriented towards the sun, and not shaded for best charging. Even a small amount of shade negates its ability to charge the battery.

I get 6 hours playback from a fully charged 2.6 Ah battery at top volume, and 10+ hours at normal listening volumes. This is with the solar panel disconnected. YMMV

Sonic Impact amp specs-

GENERAL DESCRIPTION
The TA2024 is a 15 W/ch continuous average two-channel Class-T Digital Audio
Power Amplifier IC using proprietary Digital Power ProcessingÃcï¿½Âc technology.
Class-T amplifiers offer both the audio fidelity of Class-A/B and the
power efficiency of ClassÃcâ?¬âˆ?D amplifiers.